JPH0824074B2 - Circuit and method for operating a gas discharge lamp for use in an absorption monitor - Google Patents

Description

The present invention relates to absorption monitors or detectors, and more particularly to gas discharge lamp control circuits for absorption monitors.

It is difficult to operate the gas discharge lamp efficiently because its starting voltage is much higher than its operating voltage. Typical values are 2000 volts at startup and 180 volts at operation.

In one form of lamp control circuit that seeks to solve this problem, a high potential peak is applied across the lamp to ignite the lamp, and then a lower potential AC is applied to the lamp to keep it lit. After the lamp warms up, oscillations generated by another ionization path in the lamp are reduced by the narrow blanking pulse.

In the conventional form of absorption monitor of this class, a separate circuit or modification of material circuit parameters is used to apply a high voltage starting pulse and a low voltage operating potential, the frequency is set and controlled or constant at the set frequency. Hold on to speed.

This type of conventional absorption monitor has several drawbacks. For example, (1) this often requires expensive transformers, (2) there is excessive baseline noise,
(3) Blanking pulses often interfere with ignition at start-up and warm-up, (4) energy is inefficient, heavy or bulky, and (5) lamp life is quite short.

In another form of conventional circuit, a "flyback transformer" is used to drive high voltage pulses.
This drawback is due to the poor form factor of the current through the lamp, the increased tendency to rectify to a gas discharge lamp, the short life due to harmful electrode effects, and the efficient use of the core's magnetic energy storage capacity. The transformer is relatively large and heavy because it is unattractive.

In yet another form of conventional circuit, a transformer is used,
The core saturates at the end of each cycle or half cycle when the lamp is operating and at startup. This type of conventional circuit has the disadvantage of wasting saturated power during operation and not being energy efficient.

Accordingly, it is an object of the present invention to provide an absorption monitor that uses a leakage transformer and a timing circuit to provide high voltage peaks during start-up and to control frequency during operation.
It is to provide a circuit for starting and controlling cadmium and zinc lamps.

The circuit with the lamp transformer has a primary winding and a secondary winding in circuit with the gas discharge lamp. The pulse circuit applies a pulse to the primary winding through a switching circuit that includes a current blocking device to produce a sufficiently high potential. The lamp current sensor controls the starter when a low lamp current is detected. In this device, the pulsing circuit applies a long pulse to stop the current to the primary winding after the current pulse is applied, which causes a high potential spike to be applied across the lamp to start it. The lamp is characterized by an initial ignition voltage of at least 3 times its operating voltage.

The frequency modulator increases the frequency of the pulse as the current increases to a predetermined operating value. The frequency modulator is controlled by the lamp current sensor. The sensor increases the voltage of the pulse as the current increases during start up, limiting the current after the current reaches a predetermined value.

This circuit has the additional advantage of a start timer circuit that adjusts the time period until the current reaches a second predetermined value that is less than or equal to the first predetermined value. The breaking stage has a second current
The pulse is terminated when the time expires until the predetermined value of is reached.

The synchronization and blanking circuit blanks the pulse to the primary winding of the transformer for two consecutive occurrences of the pulse and for a period of time at least equal to twice the normally operating pulse duration otherwise required. To The warm-up timer prevents blanking from initiating the application of pulses to the transformer for a time period of at least 2 seconds.

The primary winding has a center tap and first and second end taps which allow current to flow through the primary side in either of two directions. A switching circuit includes a transistor that causes current to flow in one direction while blocking current in the other direction, stopping current flow from the transformer in one direction and causing current to flow alternately from the current source in the opposite direction. By which the energy in the magnetic field alternates first in one direction and then in the other.
The secondary circuit is discharged and sends a high potential peak from the induced magnetic field to the secondary winding of the transformer. The starting control circuit that makes the current flow,
A start timer circuit for forming the voltage peak in the switching time and the inductance of the primary winding is provided. This voltage peak has an amplitude of at least 1000 volts before the lamp conducts.

This circuit is further characterized by a variable impedance circuit. The variable impedance circuit prevents high voltage peaks that exceed the peak voltage of the lamp after the lamp has ignited in response to operating current through the lamp. A frequency and current control circuit controls the current to a first predetermined level. The frequency and current control circuit has a trigger circuit that senses the current and stops the alternating flow of current from the current source each time the magnitude of the current increases to the trigger level of the trigger circuit, thereby providing a lamp. Inherently starts at low frequencies under the influence of large voltage spikes from the transformer. When the lamp is started, the frequency rises naturally to the extent required, so that the series impedance represented by the leakage inductance of the transformer causes the current to regulate to a first predetermined value.

The switching circuit has first and second power switches having first and second control elements. Each control element is connected to another end of the transformer winding. The flip flop is connected to the first and second control elements,
One of the first and second power switches is alternately driven into conduction and the other is driven into conduction, and the first and second power switches are driven into conduction.
The other power switch is driven to be conductive and the other power switch is driven to be non-conductive.

One method of operating the absorption monitor is to apply pulses of predetermined amplitude through the transformer of the lamp, to provide a dead zone of zero current amplitude between the pulses of predetermined amplitude,
Discharging current from the transformer to the lamp during the start-up period of the lamp during the dead period, and increasing the frequency of pulses through the transformer as the current through the lamp increases until the current reaches a predetermined frequency. It is characterized by each step.

Time is measured from the start of the start cycle; if the current through the lamp does not reach the predetermined amplitude, shut off the start control circuit after a predetermined time from the start of the start; pass through the transformer until the current reaches the predetermined frequency Increase the frequency of the pulse. A short blanking pulse to the lamp that prevents baseline noise is determined for a time period of at least 2 seconds from start-up and the blanking pulse is inhibited during this period.

Hereinafter, the present invention will be described in detail with reference to the drawings.

A circuit diagram of the absorption monitor 10 is shown in FIG. The absorption monitor 10 is provided with a dual beam optical system 12, a light source control circuit 14, and a detection and recording device 16 as its main components related to the present invention. The detection and recording device 16 of the absorption monitor 10 is not part of the invention except when it works with the light source 12 and a light source control circuit 14 connected to the light source 12 for control.

Dual beam light source 12 is the main component of lamp 1
8, first and second flow cells 20, 22 and first and second photo cells arranged so that the lamp 18 produces light that is focused through the flow cells 20, 22 onto the photo cells 24, 26.
It has 24,26.

Flow cells 20 and 22 are conventional, typically a reference solution flows through one flow cell and a solution containing the substance to be identified flows through the other flow cell. Light flowing from the lamp 18 through the flow cells 20,22 is converted into electrical signals in the photocells 24,26. This electrical signal is applied to the detection and recording device 16 to determine the absorbance of the solution and thereby provide information indicative of the nature of the substance in the liquid, usually in the form of chromatographic peaks. This dual beam light source 12
Are described in more detail in US Pat. No. 3,783,276. The lamp 18 is a zinc lamp, a cadmium lamp or a mercury lamp. All of these lamps are air discharge lamps that emit a specific frequency within a specific spectrum used in a monitor device.

The light source control circuit 14 is shown electrically connected to a zinc or cadmium aerial discharge lamp and includes a start control circuit 40, a current regulation circuit 42, and a frequency and drive control circuit 44 for that purpose. This frequency and drive control circuit 44 is a lamp
Outputs a pulse that starts 18 and operates. Start control circuit 40
Is connected to and operates with the frequency and drive control circuit 44 to control the high voltage start pulse applied during the start time. The current adjustment circuit 42 is a frequency and drive control circuit.
It is connected to 44 and controls operating conditions.

The frequency and drive control circuit 44 is a frequency modulation circuit 50, a gated pulser capable of controlling the frequency, and a driver circuit 52 for a switch circuit (hereinafter, referred to as “gated pulser”),
Synchronization and blanking circuit 53, switching output circuit 5
4 and a lamp transformer 56. The gated pulser circuit 52 generates pulses at a frequency which is controlled by a constant circuit during start-up and controlled by a frequency modulation circuit 50 to which it is connected during normal operation.

In one embodiment, the synchronization and blanking circuit 53 provides start timing and synchronization signals to the gated pulser circuit 52 in the manner described below. The frequency switching is controlled by the start control circuit 40, and the switching output circuit 54
Receives a pulse from the gated pulser circuit 52 and drives a lamp transformer 56. This lamp transformer 56 then supplies power to the lamp 18.

The start control circuit 40 has a lamp current detection circuit 60, an operation switch circuit 62, and a start timer circuit 64. The start timer circuit 64, the operation switch circuit 62 and the frequency modulation circuit 50 are electrically connected to the gated pulser circuit 52,
This is controlled for a fixed period of time during startup.

During start-up, the frequency modulation circuit 50 operates the gated pulser circuit 52 at a low frequency, eg 90 Hz. These long duration pulses generate a current on the primary side of the transformer.
This current rises to a large value, limited by its magnetizing inductance, and preferably saturates the core at least partially.

At the end of each pulse, the magnetic energy stored in the core of the lamp transformer 56 due to the forced current interruption is
To the high voltage pulse, while the start timer circuit 64 waits for about 4 seconds. Thereafter, if the lamp current detection circuit 60 does not detect a current corresponding to the transition to the operating state and sends a signal to the operation switch circuit 62 via the conductor 180, the start timer circuit 64 shuts off the circuit, Prevent damage to the transformer. This current, if detected, is the same as or less than the normal operating current.

When the lamp is ignited by the first four second high peak pulse, the lamp current sensor circuit 60 causes the frequency modulation circuit 50 to increase the frequency of the pulse to be generated by the lamp operating gated pulser circuit 52.

At this high frequency, the transformer core is (1) not saturated and wastes energy, or (2) as a generator of a secondary voltage proportional to the turns ratio and the primary voltage or the turns ratio and the primary current. As a generator of a secondary current inversely proportional to, does not adversely affect its operation or branch. Of course, this voltage-current characteristic is affected by lamp voltage drop, transformer resistance and leakage inductance. This leakage inductance is much smaller than the magnetizing inductance.
It can be said that the current does not flow through the magnetizing impedance during normal operation at sufficiently high frequencies.

The energy stored in the core of the lamp transformer 56 by the current source before the lamp 18 is lit up is at least on the secondary side of the transformer for commercial zinc or cadmium lamps.
It should preferably be sufficient to generate a 3000 volt voltage peak at 1000 volt startup. Also, the current must be adequate to keep the lamp on. The output circuits of the gated pulser circuit 52, the switching output circuit 54, the lamp transformer 56 and the current regulation circuit 42 are at least 10 times when operated in circuit with each other.
It is selected to have a value that produces a voltage pulse equal to 00 volts.

These high voltage pulses are provided by the current regulation circuit 42 via the primary side of the lamp transformer 56 for a time controlled by the fall time of the switching transistor in the switching output circuit 54, and Increasing the rate of current change from its initial magnitude limited by the parasitic capacitance multiplied by the other two values and the transformer core loss (Amps / sec). The other two values are (1) the magnetizing inductance (Henry) of the transformer, and (2) the transformer's 2 in series with the lamp for the number of turns on the primary side of the transformer carrying current.
It is the ratio of the number of turns on the secondary side.

FIG. 2 is a circuit diagram of the switching output circuit 54. The switching output circuit 54 includes first and second output transistors 61 and 63, and first and second RC reverse base or cutoff driver circuits 64A and 64B. Each of the RC circuits 64A and 64B has one of capacitors 66A and 66B and one of resistors 68A and 68B, respectively.
Each capacitor is connected in parallel with each resistor. One end of each capacitor is electrically connected to each base of the NPN transistors 61 and 63, and the other end is electrically connected to the input terminals 70 and 72.

The input terminals 70, 72 and the circuit common or circuit ground or "AC ground" terminal 74 are electrically connected to the gated pulser circuit 52 to receive drive pulses for output pulse generation to the transformer 56 (FIG. 1). Connected (Fig. 1),
The terminal 74 is electrically connected via a conductor 78 to the AC ground, the emitters of the transistors 61 and 63, and the anode of the zener diode 80.

To provide output pulses to the lamp transformer 56 (first
The first and second output terminals 82 and 84 are electrically connected to the respective collectors of the transistors 61 and 63 via the forward resistances of the reverse blocking diodes 86 and 88, respectively. It is also electrically connected to the cathode of Zener diode 90 via each one of diodes 92 and 94. The cathode of zener diode 80 is electrically connected to the anode of zener diode 90 to form an overvoltage clamp circuit.

Reverse blocking diodes are not normally found in what appears as a similar circuit commonly referred to as an "inverter circuit". These diodes ensure voltage spikes. Voltage spikes are not desirable in common inverter circuits. The overvoltage clamp circuit limits the voltage spike to 200 volts on the primary side of the lamp transformer 56 (Fig. 1) when the lamp 18 does not ignite, and the secondary voltage exceeds 3200 volts due to the transformer ratio of 16: 1. Prevents rapid damage to the transformer due to.

In start mode, transistors 61 and 63 receive pulses from gated pulser circuit 52. Due to the charge stored in the capacitor 66A or 66B of each base, one of the transistor bases receives a positive pulse and the other receives a negative pulse. The negative base energization provided by capacitors 66A and 66B rapidly switches transistors 61 and 63 when they are turned off. This is important for providing high voltage pulses because the amplitude of the voltage pulse depends on the rate of change of current. After this, the energization from the gated pulser circuit 52 is reversed, so that the transistor has its emitter grounded so that both transistors are driven alternately and driven to conduction.

Since the negative going pulse applied by the gated pulser circuit 52 to terminals 70 and 72 has a duration of 5 microseconds longer than the positive going pulse, the gated pulser circuit 52 inputs 70 and 70 to the switching output circuit 54.
The negative drive pulse on one of the 72's overlaps, creating a 5 microsecond time period such that the bases of both transistors 61 and 63 are negative. This is done to ensure that both transistors do not conduct simultaneously during the transition, despite the fact that the turn-off time is usually longer than the turn-on time.

During the start-up phase of one cycle, transistor 61 and
When one of the 63 is conducting, current flows from one of the terminals 82 or 84 connected to the transformer 56 (Fig. 1) to ground through the conducting transistor. During this time, energy is stored as a magnetic field due to the magnetic flux in the transformer core, thus producing a high voltage positive peak when a dead time period occurs that terminates the current flowing through this transistor. The collector of the transistor is a Zener diode 8 up to 200 volts to the grounded center conductor 74.
Clamped by 0 and 90. This fairly narrow 200 volt pulse is boosted to about 3,000 volts on the secondary side by a 16: 1 lamp transformer 56 (FIG. 1) where it is applied to lamp 18 to ignite it.

The 200 volt negative pulse generated by the action of the transformer at the opposite end of the transformer is not applied to the other transistor. This is a reverse blocking diode
This is because 86 or 88 is reverse biased. Such diodes are not normally used in switching power supplies,
It is an important factor in forming the high voltage starting pulse in the embodiment shown in the drawings. Without these, the pulse would be undesirably clamped at a relatively low voltage due to reverse conduction in the transistor.

During the start-up cycle, the transformer 56 saturates and the transformer is chosen with sufficient characteristics for this saturation. Normally, it has a smaller magnetizing inductance and a smaller saturation flux density than the transformers which have been purposefully selected for the starting frequency used, and are therefore often less expensive transformers. The starting frequency of 100Hz is about
It is used with a magnetizing inductance of 0.8 henries and a 24 volt DC voltage source for a particular transformer that core saturates with a 0.5 ampere primary current when there is no current on the secondary side. It has been found that increasing the current through the saturating core before the end of the half cycle produces a more energetic high voltage starting pulse. At the end of each 1/2 cycle, the core saturates at about 0.7 amps.

For this particular transformer, the current is
An operating frequency of 1000 Hz is used in the example adjusted by, and an operating frequency of about 5000 Hz is used in the example where the current is adjusted by the leakage inductance of the transformer.

In the embodiment where the operating current to the lamp is regulated by the operating frequency, the actual useful operating frequency is determined by the leakage inductance of the transformer, which is about 20 millihenries. This inductance is an economical value. This is because this value is typical of low cost laminated silicon-iron core high voltage transformers with separate bobbins for the primary and secondary windings. This frequency is easily adapted to the leakage inductance of this type of transformer designed with the lowest cost in mind, rather than for some extreme values of leakage inductance that differ from the simplest and most economical size. Can be adjusted.

During normal operation, once the lamp has begun to conduct, the gated pulser circuit 52 will pulse at a higher frequency under the control of the lamp current detection circuit and the frequency modulation circuit.
Under these conditions the lamp transformer 56 (Fig. 1) will not saturate. This is because at high operating frequencies, the magnetizing current of the transformer does not have enough time to reach saturation. The operating voltage of the lamp is only about 200 volts, so most of the current in the primary circuit of the transformer is transferred to the secondary circuit.

In this mode of operation, when current is flowing from the current regulator circuit 42 through either of the primary loops, the current regulator circuit 42 in one embodiment provides a zinc or cadmium lamp with a substantially constant 40 milliampere average, In another embodiment, the mercury lamp is given an average of 18 milliamps. As a result, current alternately flows through terminals 82 and 84, respectively through transistor 63 to ground and then through transistor 61 to ground, which ramps the transformed AC output by lamp transformer 56. 18 (Fig. 1). Lamp power is usually more closely proportional to average current, not RMS (rms value) current. This is because the lamp voltage hardly changes with respect to the current over the entire normal current operating range after lighting.

The impedance of the load connected to the secondary side is over 200 KΩ in the unlit tube, and the energy of the collapse field is sufficient to generate at least 2 KV across it for about 1 ms. For some lamps it is appropriate to apply 1000 volts for 10 microseconds at high impedance. This magnetic field is typically generated by the rise of the primary current during a period of less than 5 ms. For this condition, the inductance and primary current are sufficiently large and the losses are sufficiently small to generate a sufficiently large energy field.

FIG. 3 is a circuit diagram of the gated pulser circuit 52. The circuit 52 has an output stage 100, a control stage 102, a timing stage 104 and a shutoff stage 106.

This gated pulser circuit 52 is a Motorola Semiconduct
This is a SG3525A type circuit that is commercially available from Or Division (Phoenix, Arizona). Although this commercial unit is purchased and used to provide the elements of Figure 3, the actual commercial "pulse width modulator" used as a gated pulser has additional elements, but for simplicity It is omitted from FIG. This pulse width modulator is a publication of Motorola Corporation, "Pulse Width Modulator Control 10 Circuit".
cuit) SG1525A / SG1527A ”.

In order to apply a base current to one of the transistors 61 and 63 of the switching driver circuit 54 (FIGS. 1 and 2) and remove a base current from the other, and to drive the lamp transformer 56, the output drive circuit 100 A gate 11 connected to the transistor output circuits 116 and 118 detailed in the Motorola Manual above and forming a totem pole.
It has 2 and 114. This circuit provides fast shutoff and dead time when connected in the push-pull configuration of FIG.
This dead time can be adjusted between the two stages of the output to count the turn off times of transistors 61 and 63.

With this configuration, the transistor cascade output circuit
116 provides a turn-off drive current to or draws current from input terminal 70 (drives it to turn-off), and cascade transistor 118 provides a current to input terminal 72 or draws a current therefrom. The time to draw the current is a little longer than the drive time, and both transistors 61 and 63 (second
(Figure) should not be conducted at the same time.

In order to control the output drive circuit 100, the control circuit 102 has a flip-flop 120, a latch 122 and a comparator 124. Comparator 124 has a first input 132 connected to capacitor 146 and a second input 13 connected to the output of amplifier 150.
0 and a third input 128A connected to the collector of transistor 160. If either the second input 130 or the third input 128A of the comparator 124 is at a lower potential than the first input 132, the comparator will have its output connected to the set input terminal of the latch 122. Generates a "set" signal to. A current source 128 connected to the collector of transistor 160 causes the third input 128A of comparator 124 to go "high" when transistor 160 turns off.

Latch 122 is reset by a pulse from oscillator 140 of synchronization circuit 104 on conductor 134. This pulse also
Change the state of flip-flop 120, or "toggle"
Then, it causes the OR gates 112 and 114 of the output drive circuit 100 to send a pulse. In another embodiment (FIG. 14), this pulse is applied via conductor 416A in the manner described below. The set output of flip-flop 120 is electrically connected to OR gate 112 and the reset output terminal is connected to OR gate 114 to open one gate and close the other, depending on the state of flip-flop 120. Therefore, the outputs 70 and 72 are alternately turned on and off. The output of the latch is connected to OR gates 112 and 114 so that a pulse is sent through OR gate 112 or 114 in response to either state of flip-flop 120. The latch 122 is the synchronization circuit 104.
Give dead time in sync with.

To synchronize operation and provide repeatable lamp re-ignition conditions, the synchronization circuit 104 includes an oscillator 140, a transistor 144, an external timing frequency capacitor 146, a dead time setting resistor 144B and conductors 148, 149, 416. . The conductor 134 switches the flip-flop 120 to a transistor.
A blanking pulse is applied to turn off 61 and 63 (Fig. 2).

In all embodiments, conductor 144A controls the base of NPN transistor 144 whose emitter is grounded. In one embodiment, the collector of NPN transistor 144 is connected to frequency control capacitor 146 via resistor 144B. Conductor 144A receives the positive pulse from oscillator 140 as oscillator 140 sends the positive output pulse on line 134 to flip-flop 120. As conductor 144A goes positive, transistor 144 conducts and capacitor 146 discharges through resistor 144B and transistor 144.

The capacitor 146 is a synchronization and blanking circuit 53.
(Fig. 1) is charged by current through line 149,
It provides synchronization and blanking periods. The flow of current through conductor 148 under the control of frequency modulation circuit 50 (FIGS. 4 and 1) changes the frequency of oscillator 140, thereby providing a starting frequency below the operating frequency, As a result, it provides a high voltage for starting the lamp. As the current in conductor 148 increases, the frequency of oscillator 140 increases,
As the current in conductor 148 decreases, the frequency of oscillator 140 decreases. The operating frequency is set by the frequency of oscillator 140 (FIGS. 1 and 3).

In order to turn off the circuit and control the start-up time and turn-off time, the shut-off stage 106 includes first and second shut-off stages.
It has a differential amplifier 150 having input terminals 152 and 154 and a cutoff circuit 156. The cutoff circuit 156 is an NPN transistor 1
Has 60. The base of this transistor 160 is a resistor 1
Connected to terminal 76 via 62, collector is a constant current source 128
Is connected to one input of the comparator 124, and the emitter is a resistor 164
Connected to circuit ground via. Terminal 74 is connected to circuit ground.

Conductor 76 is grounded in one embodiment and connected to conductor 416 for gating and synchronization in another embodiment. When conductor 416 receives a positive gate pulse, oscillator 140 turns on transistor 144 and causes the capacitor to turn on.
Discharge 146. The oscillator 140 has a line 134 and gates 112, 11
Turn off the output circuits 116, 118 via 4. A positive gate pulse on conductor 76 turns on transistor 160,
Set latch 122 via line 128A to comparator 124.
This ensures that the gates 112, 114 hold the output circuits 116, 118 off for the entire gate pulse.

Conductors 152, 154 control amplifier 150 and also control comparator 124 via line 130. Comparator 124 is also controlled by lines 128A and 132. The frequency is about 10 at the start in one example.
Controlled to an operating frequency between 0 and 130 Hertz to 750 and 1100 Hertz.

Amplifier 150 compares the output potential from run switch circuit 62 received via conductor 152 with the reference potential from start timer circuit 64 received via conductor 154 (first).
Figure). In one embodiment, the frequency is controlled by controlling the current exiting oscillator 140 on conductor 148, which in turn
The charging current on 149 is changed to change the charging rate of capacitor 146.

When the voltage on line 149 reaches a predetermined magnitude, this voltage triggers oscillator 140 to produce a positive voltage on lines 134 and 144A.
Print on top. This turns on transistor 144, discharging capacitor 146 via resistor 144B. Line 1
When the voltage on 49 drops to the second predetermined magnitude, oscillator 140 removes the voltage from lines 134 and 144A and the cycle repeats so that capacitor 146 recharges.

If the lack of current through lamp 12 (FIG. 1) indicates that it has not begun to conduct in 4 seconds as determined by the start timer circuit, conductor 152 is at a potential near ground potential. , While conductor 154 remains positive while comparator 124 receives a negative potential via conductor 130.
This sets the latch 122 to shut off the drive circuit.

The current applied to conductor 148 by the frequency modulation circuit (FIG. 1) is connected to oscillator 140 and changes the charging current of capacitor 146 to change the frequency of oscillator 140. The signal from the frequency modulation circuit 50 is the lamp current detection circuit 60 (Fig. 1).
Under the control of the frequency from the oscillator 140 smoothly and gently during operating conditions from 130 Hertz at the start to 750-1100
The Hertz range is increased, thereby controlling the switching of flip-flop 120 via oscillator 140 and the frequency of the pulses provided to switching output circuit 54 (FIG. 1).

FIG. 4 is a circuit diagram of the frequency modulation circuit 50. This circuit
50 has an NPN transistor 170 and a capacitor 178. Conductor 148 electrically connects oscillator 140 (FIG. 3) to the collector of transistor 170 via resistor 172. The emitter of transistor 170 is connected to ground via resistor 176. Resistor 174 provides a minimum current on line 148 when transistor 170 is not on at all, which causes oscillator 1
Generates low frequencies from 40.

The base of transistor 170 is electrically connected to ground via capacitor 178 and to terminal 180 via resistor 182. Terminal 180 is electrically connected to the lamp current detection circuit 60 (Fig. 1) to control the frequency of the gated pulser circuit 52 (Fig. 1) during start-up to run and during run. Conductor 148 is oscillator 140 (Fig. 3)
It is connected to the frequency adjusting resistor input terminal of and controls the frequency of the oscillator 140.

The potential applied to terminal 180 indicates the flow of current and controls the impedance of transistor 170. As the current increases, the impedance of transistor 170 decreases, grounding resistors 176 and 172 in parallel with resistor 174. This circuit determines the charging rate of capacitor 146 and raises the frequency of oscillator 140 (FIG. 3) as the current increases to its operating current. The resistance of resistor 174 is large and can be much larger than the resistance of resistors 172 and 176, so that in practice the frequency of the oscillator can be switched over a wide range.

The RC time constant of capacitor 178 and resistor 182 is large enough that the frequency of the oscillator does not rise fast enough that the lamp remains on during the start-to-run transition. In one example, it has been found that an RC time constant of 1/2 second is sufficient.

FIG. 5 is a circuit diagram of the lamp current detection circuit 60. The circuit 60 has a lamp rectification prevention unit 190, a current detection unit 192, and a heater unit 194. Terminal 196 is electrically connected to lamp 18 for receiving a current through lamp 18 and is connected to anti-rectification 190. Positive potential source 198 is heater 194
Is electrically connected to one end of. The other end of the heater section 194 is connected to the circuit ground, and the current detection section 19 is connected via a conductor.
Connected to two. The potential source 198 is on only when the device is turned off. The connection to the heater section 194 when the absorption monitor is turned off reduces the warm-up time by preheating the device to near operating temperature before it is turned on. This does not affect the operating temperature of the absorption monitor, as it is automatically turned off when the absorption monitor is turned on.

The current detector 192 is a filter capacitor 202, a diode
204, and first and second resistors 206 and 208. Resistor 208 is electrically connected to conductor 200, which is connected to ground and to one end of capacitor 202. The other end of the resistor 208 is electrically connected to the non-rectifying unit 190 and one end of the resistor 206. The other end of the resistor 206 is connected to the other end of the capacitor 202 through the forward resistance of the diode 204 and the terminal 180.
Is electrically connected to

The lamp rectification prevention unit 190 has first and second Zener diodes 210 and 212, and a capacitor 214. The Zener diodes 210 and 212 have their anodes connected to each other and their cathodes electrically connected to another plate of the capacitor 214. The cathode of Zener diode 212 is electrically connected to terminal 196, and the cathode of Zener diode 210 is connected to one end of resistor 206 and resistor 208.
Is electrically connected to one end of.

The heater portion 194 has a plurality of resistors, each of which can be modified to fit different types of lamps. The resistors provide different heating resistance values to establish the proper standby temperature when the absorption monitor is turned off.

In operation, the current through lamp 18 flows through terminal 196 and primarily through resistor 208 to conductor 200. This current is typically an AC current, and if the lamp has the undesirable property of shortening its operating life due to commutation, the capacitor 214 will in the opposite direction receive a charge to stop such commutation. Zener diodes 210 and 2
Twelve protects capacitor 214 from unusual total fault conditions.

Diode 204 rectifies the voltage drop across resistor 208 due to this current in the form of alternating polarity pulses.
This current charges the capacitor 202 after a few pulses so that it actually reaches a predetermined potential when current is flowing through the lamp 18 (FIG. 1). This potential provides a signal on conductor 180 indicating that the lamp has ignited.

The resistor 206 determines the charging rate. This speed produces a potential across capacitor 202 which is provided to terminal 180 as a signal to run switch circuit 62 (Fig. 1) and to frequency modulation circuit 50 (Fig. 1). This signal indicates whether the lamp 18 is non-conducting during its starting phase, or immediately after its initial ignition, or whether the lamp is at rated current.

FIG. 6 is a circuit diagram of the operation switch circuit 62. This circuit 62 comprises first and second NPN transistors 220, 222 and first, second and third output terminals 224, 226 and 228.
have. The base of the transistor 220 is electrically connected to the terminal 180 via the resistor 230, and the base of the transistor 222 is electrically connected to the terminal 180 via the transistor 232. The collector of the transistor 220 is the output terminal 224.
And the emitter is electrically connected to terminal 226. The output terminal 228 is electrically connected to the collector of the NPN transistor 222, and the emitter is grounded.

Run switch circuit 62 receives a signal on terminal 180 indicating that the current through lamp 18 is at least the magnitude of the start, and the signal is (1) start timer circuit 64.
(Fig. 1) shows the starting conditions of the lamp 18 to the output terminal 22
4, 226, (2) to the second output of terminal 228 to start timer circuit 64, and (3) to gated pulser circuit 52. The transistors are identical and both base resistors have
It has a resistance value of 22 KΩ. At the same potential, transistors 220 and 222 send corresponding signals to start timer circuit 64 which interprets these signals.

FIG. 7 shows the start timer circuit 64. This circuit
Reference numeral 64 has an RC time constant circuit 240, one NPN transistor 242 and an output circuit 244. In the transistor 242, the emitter is grounded and electrically connected to the terminal 226, and the collector is electrically connected to the terminal 224. Transistor 242
The base of is electrically connected to resistor 248 and capacitor 250. These are the main timing elements of the RC time constant circuit 240.

In order to detect a signal indicating a start failure after a delay of 4 seconds or more and to send this signal to the gated pulser circuit 52, the RC time constant circuit 240 includes a first resistor 246 and a second resistor 24.
8. It has a capacitor 250, a diode 252 and a resistor 254. Resistor 248 is electrically connected at one end to the base of NPN transistor 242 and to ground through resistor 246, and at the other end to the reverse resistance of diode 252 and to one end of timing capacitor 250. . The other end of timing capacitor 250 is connected to terminal 228 and resistor 25
It is electrically connected via 4 to a positive reference potential 256.
The reference potential 256 is provided by the Motorola SG3525A used as the gated pulser circuit 52. The reference potential 256 is electrically connected to the output terminal 224 via the resistors 258 and 260.

The output section 244 includes a terminal 154 electrically connected to one input of the amplifier 150 (FIG. 3) and an amplifier 150 (FIG. 3).
And a terminal 152 electrically connected to the other input of the. The terminal 152 is connected to the reference voltage 256 via the resistor 260,
And is electrically connected to the terminal 224 via the resistor 258. Terminal 154 is connected to ground through resistor 264 and resistor 266.
At a reference voltage generated by electrically connecting to a positive reference potential source 256 via.

This transistor 242 keeps terminal 152 lower than terminal 154 because transistor 242 is initially conducting at start-up due to the current flowing through the RC time constant circuit 240 to the base. R
C circuit 240 has a time constant of 4 seconds, after which time transistor 242 shuts off, causing terminal 152 to rise above the level of terminal 154, and transistor 220 (first connected to terminal 224). If (Fig. 6) does not become conductive, this circuit is cut off. Transistor 220 conducts when it receives a sufficiently large signal on terminal 180, indicating that lamp 18 is on (FIGS. 1 and 5). When the lamp 18 (Fig. 1) is turned on, the capacitor 250, the diode 252, the transistor
It is immediately discharged via 222 (Fig. 6) and terminal 228.
This allows the start-up cycle to be repeated after inadvertent interruption of the mains supply.

FIG. 8 is a circuit diagram of the current regulator 42. This adjuster 42
Has a bias and control circuit 270, a variable impedance circuit 272, and a constant current output circuit 274. The bias and control circuit 270 determines the current through the bias and control circuit 270 from the primary side of the lamp transformer 56 (FIG. 1) by the characteristic of the value of the variable impedance circuit 272 and the elements of the circuit 270. In order to maintain the set value of the variable impedance circuit 272, a potential proportional to the current controlling this variable impedance circuit 272 is established.

The variable impedance circuit 272 is a circuit that generates a constant current regardless of the load voltage within a given range. In the embodiment using the frequency modulation circuit 50 of FIG. 4, the output current is
The potential across the series sense resistor is maintained to be equal to the potential of the fixed reference potential by changing the internal impedance. This circuit is National Semiconducto
This is the LM337 sold by r, Inc. This integrated circuit is marketed by National Semiconductor as a voltage regulator, but the manufacturer's printed matter recommends using it as a current regulator with the input and output terminals reversed as shown in FIG. Suggests. The “IN” terminal of this integrated circuit (272) is connected to the constant current output circuit 274.

The bias circuit 270 includes first and second output conductors 276, 278, a potential source 280, a switch 282, and a resistor bridge 284 to provide the same set point voltage to different lamps requiring different currents. ing. Switch 282 changes the impedance of resistor bridge 284 by shorting a resistor and regulates the current to the lamp between different types of lamps 18, such as zinc halide lamps and mercury lamps.

The bridge circuit 284 includes a potentiometer 286, a first resistor 288, and a second resistor 29 to provide a bridge voltage divider.
It has 0 and a third resistor 292. First output conductor 27
8 is connected to the variable impedance circuit 272 at one end, and is connected to (1) one end of the resistor 292, (2) one end of the resistor 290, and (3) one end of the resistor 288 at the other end. The other end of resistor 292 is connected to the fixed contact of switch 282 and the other end of resistor 290 is electrically connected to the armature of switch 282, forming a parallel path between the ends of these two resistors. This changes the resistance value of the bias circuit 270. This change in resistance allows another lamp to fit the absorption monitor 10.

The reference potential source 280 is electrically connected to the armature of the switch 282 and to one end of the potentiometer 286. The other end of the potentiometer 286 is electrically connected to the other end of the resistor 288. The center tap of potentiometer 286 is electrically connected to output conductor 276 and a bias voltage is set between conductors 276 and 278 to variable impedance circuit 272.

The output circuit 274 includes a terminal 294 electrically connected to the lamp transformer 56 (FIG. 1), a first impedance circuit 296,
And a second impedance circuit 298. Terminal 2
94 is electrically connected to the center tap of the lamp transformer 56 (Fig. 1), and supplies the current from the switching output circuit 54 through one half or the other half of the primary winding of the lamp transformer 56. Control, which keeps the current constant. Impedance circuits 296 and 298 create an impedance between variable impedance circuit 272 and terminal 294 to protect the circuit and maintain the current at the desired set point.

The first impedance circuit 296 has a capacitor 300 and a resistor 302. The input terminal 294 is electrically connected to one plate of the capacitor 300, one end of the resistor 302, and the input terminal of the variable impedance circuit 272.
The other end of the resistor 302 and the other plate of the capacitor 300 are
Electrically connected to AC ground to shunt transient AC current to ground.

The second impedance circuit 298 includes first and second capacitors 304 and 306, a resistor 308 and a diode 310. The terminal 294 is electrically connected to the input end of the variable impedance circuit 272, the anode of the diode 310, and one plate of the capacitor 304 via the impedance circuit 296. The cathode of diode 310 is electrically connected to one plate of capacitor 306 and to one end of resistor 308. The other plate of capacitors 304, 306 and the other end of resistor 308 are electrically connected to AC ground to shunt the voltage spike to ground.

Capacitor 306 can be much larger than capacitor 304 and can absorb high energy voltage spikes without exhibiting low impedance at terminal 294. Capacitor 30
If 6 is low impedance, the constant-current performance of the circuit is that capacitor 306 charges rapidly to a high voltage and capacitor 3
Will be degraded by discharge through 04. But,
Such degradation in current operation requires the impossible reverse conduction of diode 310. A resistor 308 connected across capacitor 306 dissipates the energy of each spike stored in capacitor 306 so that capacitor 306 is ready to absorb the next spike.

In the current adjusting circuit 42, each half of the switching output circuit 54 (Figs. 1 and 2) has terminals 82 and 84 (Figs. 1 and 2).
Through the terminal 29 of the current regulating circuit 42 (Figs. 1 and 8).
The current flow is controlled so as to give the current flowing to 4.
Thus, the value of the current amplitude set in the current regulation circuit 42 controls the current passing through either half of the primary side of the lamp transformer 56 (FIG. 1). This is the switching output circuit 54
It controls the flow of current from the output terminal 82 or 84 (FIGS. 1 and 2).

With this type of control, the potential on the secondary side of the lamp transformer 56 is controlled by the lamp 18 (FIG. 1) and the lamp does not have a constant start or has an absolutely flat operating voltage-current characteristic. Unless otherwise provided, the potential used to light the lamp 18 for start-up or operation can be altered to some extent by the current regulation circuit 42.

FIG. 9 is a circuit diagram of the variable impedance circuit 272. This circuit 272 is based on Natioral Semiconductor LM137 / LM23
It is composed of the negative voltage regulator of 7 / LM337. This regulator is used as a positive current regulator with inverted nominal input and output terminals in this embodiment.

Positive voltage regulators such as National Semiconductor LM317, which are connected as positive current regulators without inverting the input and output terminals, do not work well. This is line 294
This is because it is considerably disturbed by the above electrical fluctuation. Na
tonal Semiconductor LM137 / LM237 / LM337 holds terminal 278 at a constant negative 1.25 volts with respect to terminal 276.

The current flowing from the current regulation circuit 42 through the transformer terminals 82 and 84 (FIG. 1) of the lamp transformer 56 is at a value determined by the potential difference applied across terminals 276 and 278. This controls the impedance between terminals 278 and 294. This current remains constant regardless of lamp voltage variations because this impedance increases rapidly in response to an increase in the voltage drop between terminals 276 and 278 that is proportional to the current. This is set by the voltage between conductors 276 and 278 via bias and adjust circuit 270.

FIG. 10 is a block diagram of the synchronization and blanking circuit 53. This circuit 53 includes a warm-up timer 413 and a plasma stabilized oscillator circuit 415. The synchronization and blanking circuit 53 includes a gated pulser circuit to shut off the lamp every 100 ms for a 5 ms time period.
52 (Fig. 1) is given a periodic blanking or gating pulse, but these pulses are applied for a warm-up time of 2 minutes and 16.5 seconds to avoid disturbing the lamp 18 (Fig. 1). Delay. What is important about this warm-up time is that it is long enough for the lamp to warm up sufficiently for a re-ignition voltage that is still greater than the arc holding voltage but much less than the initial ignition voltage.

The warm-up timer 413 includes a 14-bit binary counter 412, an NPN transistor 426 and a diode 432 to inhibit blanking pulses during the warm-up period. Binary counter 412 is a Motorola MC14020B 14 bit binary counter manufactured by Motorola. This clock input terminal is electrically connected to one end of the resistor 442 and the anode of the diode 432.

The clock pulse source is connected to terminal 452. This pulse source is the AC mains frequency signal normally obtained from a conventional AC mains operating power supply for DC used by the rest of the circuit. This terminal connects resistor 442 to the other end of resistor 442 and resistor 446 to provide a 60 Hz clock pulse to the binary counter clock input terminal when power is applied to the absorption monitor 10 (FIG. 1). Connected to ground through.

The reset input terminal of the binary counter is connected to one end of the resistor 440 via the capacitor 438 and the resistor 436 in series and a positive 15
It is electrically connected to the volt power supply. The other end of the resistor 440 is grounded. The RC circuit differentiates the signal from the positive potential source 437, which resets the binary counter when power is first applied to the absorption monitor 10 (Fig. 1) and applies a positive 15 volts to terminal 437. give.

The base of the transistor 426 is the output 43 of the binary counter 412.
It is electrically connected to 4A, its emitter is grounded and its collector is (1) to the cathode of diode 432, (2) via lead 435A in warm-up timer circuit 413, and via terminal 346 and plasma stabilization. Electrically connected to plasma stabilized oscillator circuit 415 via lead 435 in stabilized oscillator circuit 415 and (3) to positive 5 volt voltage source 433 via resistor 430.

The operation will be described. When power is applied, a spike is generated by the differentiating circuit from the positive 15 volt voltage source 437, which resets the binary counter. The differentiating circuit includes resistor 436, capacitor 438 and resistor 440. A clock pulse is applied from terminal 452 of the main power supply to the clock input terminal of binary counter 412. This causes the clock pulse to take 2 minutes 16.5 seconds on the 60Hz mains or 2 minutes 43.8 seconds on the 50Hz mains until the positive output pulse from counter 412 on lead 434A is applied to the base of transistor 426 via resistor 434. The inter-counter 412 starts counting.

A positive pulse applied to the base of NPN transistor 426 causes it to conduct, lowering its collector voltage and pulling the clock input source to a lower potential through diode 432, which causes the counter to count further. Prohibit This low collector voltage is a conductor
A low signal is sent to the plasma ballast oscillator circuit 415 via 435. At this point, the plasma ballast oscillator circuit 415 is
Begin to generate 5 ms pulses at 100 ms intervals to stabilize the plasma within 8 (Fig. 1).

The plasma ballast oscillator circuit 415 includes a pulse generator 414 and a transistor 418 to generate a blanking pulse upon receipt of a low signal on conductor 435. The pulse generator 414 is an LM555 timing circuit manufactured and sold by National Semiconductor. It can be tuned to provide time delays and pulses over a wide range of this pulse, as well as National Semiconductor Corpo
It is described in detail in the printed material commercially available from ration.

To prevent blanking pulses from occurring during the warm-up period, the NPN transistor 418 has an emitter grounded and a collector connected through a resistor 424 to a positive 15 volt voltage source.
22 electrically connected to the base via resistor 428 to conductor 4
Electrically connected to 35. Output 4 of pulse generator 414
20A is electrically connected to the base of the transistor 418 via the conductor 420A and the resistor 420, and further connected to the blanking pulse output terminals 76 and 416 which are electrically connected to the collector of the transistor 418. As a result, conductor 4
When 35 is positive during the warm-up period under the control of the binary counter 412, transistor 418 conducts, terminals 76 and 416 are at ground level, and the output conductor of pulse generator 414.
Not affected by pulses on 420A. In this form of embodiment, the conductor 149 of FIG.
Do not connect 3 to the gated pulser circuit 52.

At the end of the warm-up period, conductor 435A, terminal 346
And when conductor 435 drops to a low value, pulse generator output lead 420A is also low and the output of conductor 149 is a positive voltage source 422.
If it becomes positive under the influence of, the transistor 418 becomes non-conductive. A 100 millisecond "on" pulse on conductor 420A now drives transistor 418 into conduction, causing the potential on line 424A to drop to ground level. A negative going 5 ms “off” pulse on conductor 420A closes transistor 418 under the control of pulse generator 414 and outputs a positive pulse at terminal 76.
And 416. This is the gated pulser circuit 52
Turn off the output circuits 116 and 118 of FIG. 3 (FIG. 3), and at the same time turn off the switching output transistors 61 and 63 (FIG. 2) and the transformer windings of terminals 82 and 84 (FIG. 1).
This turns off lamp 18 for 5 milliseconds.

To control the timing of pulse generator 414, positive voltage source 417 is connected in series with resistors 419, 421 and capacitor 4 in series.
Electrically connected to ground through 23, pulse generator 414
Controls the threshold and trigger value for self-oscillation of. This pulse generator circuit is substantially as described in the manufacturer's printed matter applications. Capacitors 425 and 429 prevent electrical noise interference problems. In order to generate the vibration in the pulse generator 414 at the proper timing, the conductor 431 connects each one of the resistors 419 and 421 to the pulse generator 414.
And provide discharge of capacitor 423 through resistor 421 at the end of each pulse cycle. Conductor 437 has resistance 42
The output signal and the trigger signal are applied to the flip-flop in the pulse generator 414 which is connected to the capacitor 1 and the capacitor 423 and is a part of the feedback oscillation loop. Conductor 433 is capacitor 429
Is connected to a pulse generator 414 to generate a high frequency pulse. The capacitance of capacitor 429 is 10% that of capacitor 425 and both capacitors remove voltage spikes from the circuit.

FIG. 11 is a circuit diagram of a National Semiconductor TTL (transistor-transistor logic) type LM555 pulse generator 414. This pulse generator 414 has a flip-flop 437.
It has an A, a first comparator 439, a second comparator 441, and an NPN transistor 443. To form an oscillator circuit,
The transistor 443 has a collector electrically connected to the conductor 431 and a base electrically connected to the output end of the flip-flop 437A. The conductor 437 is electrically connected to the non-inverting input terminal of the comparator 439 and to the inverting terminal of the comparator 441.

With these connections, the signal from the output of flip-flop 437A discharges current from capacitor 423, which is charged by voltage source 417 (FIG. 10). at the same time,
This applies a voltage pulse via conductor 437 to the non-inverting terminal of comparator 439 and to the inverting terminal of comparator 441, resetting flip-flop 437A. The flip-flop 437A starts another cycle in response to the charging of the capacitor 423 (Fig. 10).

The constant potential from the potential source 417 applied to the non-inverting input terminal of the comparator 439 and the inverting terminal of the comparator 441 is equal to that of the capacitor 4
Holds a constant threshold value that is switched through an oscillator circuit having 23 (FIG. 10). The magnitude of the capacitance and resistance are adjusted to control the on / off cycle and frequency of the pulse generator 414.

If there is no blanking circuit, the lamp tube 18
The path of the ions inside changes course with a continuous, rhythmic, periodic oscillation that is squeezed to generate low-frequency optical noise in the tube. The blanking pulse extinguishes this vibration,
This prevents noise.

FIG. 12 is a circuit diagram of the plasma stabilized oscillator and synchronization circuit 320. This circuit 320 includes an operational amplifier 322, an NPN transistor 324, a first capacitor 326, and a second capacitor 32.
8, having a first diode 330 and a second diode 352.

The inverting input terminal of the operational amplifier 322 is (1) Feedback resistor 3
36 and its output through a series-connected resistor 338 and diode 352, and (2) AC via a capacitor 328
Electrically connected to ground. The non-inverting input terminal of the operational amplifier 322 is (1) AC grounded via the resistor 340,
(2) It is electrically connected to the output end of the operational amplifier 322 through the feedback resistor 342, and (3) to one end of the capacitor 326.

The output terminal of the operational amplifier 322 has feedback resistors 342, 336 and 338.
In addition to being electrically connected to the base of the transistor 324, it is electrically connected to the base of the transistor 324 via the forward resistance of the diode 330, the resistance 344 and the resistance 348 in series. The other pole of the capacitor 326 is electrically connected to the terminal 70.

To connect the synchronization circuit 320 to the gated pulser circuit (FIG. 1), the collector of the transistor 324 is a conductor 149.
B and the diodes 324A and 324B are electrically connected to the terminal 149A. Terminal 149A is connected to conductor 149 in one embodiment (FIGS. 1 and 3). Diode 324A
And 324B are terminals of the gated pulser circuit 52 (Fig. 3).
The high voltage applied to 152 (FIG. 3) causes the comparator 124 to set the latch 122 and turn off the output transistors 61, 63, shutting off the current supplied to the primary side of the transformer 56 as previously described. Have a sufficient voltage drop to The emitter of transistor 324 is electrically connected to AC ground. In an embodiment using this configuration, the conductor
76 and 416 have been omitted from FIG. 1 and replaced with conductor 1 of FIG.
49 are used.

With these connections, a stabilized oscillator and a synchronization circuit
320 generates blanking pulses to stabilize the lamp plasma and applies these pulses to the gated pulser via terminal 149A to synchronize these pulsers to the gated pulser circuit 52 (FIG. 1). By applying a low synchronization pulse to terminal 149A, capacitor 14
6 is discharged (Fig. 3) and two drive terminals 70 or 72
One of them is locked "on" (high).

This low amplitude sync pulse on terminal 149A holds output transistor 61 or 63 on during the blanking pulse. The high current obtained causes sufficient energy to be stored in the core of the lamp transformer 56 (FIG. 1) in order to provide a voltage large enough to re-ignite a lamp that is not warmed up. In this way, warm up timer 41
3 is not needed at all (Fig. 10). A return pulse is applied from the gated pulser circuit 52 to the stabilized oscillator 320 via the terminal 70 (FIGS. 1, 2, and 12). By exchanging this pulse on conductors 149A and 70 (Fig. 12),
The oscillator 140 of the gated pulser circuit 52 (see FIGS. 1 and 3).
(Figs.) And 414 (Figs. 10 and 11) maintain a certain phase relationship. Otherwise, the beat signal is generated by the frequency of the stabilized oscillator and the frequency of the gated pulser circuit 52, which causes optical noise.

The circuit of FIG. 12 may be used with the circuit of FIG. 1 or with another circuit. In this alternative circuit, the current regulator 42 (Fig. 1) is only used during start-up, and the frequency of operation is high enough that the leakage inductance of the transformer limits the operating current. Controlled by another circuit. This circuit does not require the start-up timer circuit 64 or the frequency modulation circuit 52, but the use of the frequency control circuit causes the operating frequency to rise slowly.
These simplifications are possible because this circuit provides a high relighting voltage after blanking and this circuit mutually synchronizes the synchronization and blanking circuit 53 with the gated pulser circuit 52.

FIG. 13 is a circuit diagram of the frequency control circuit 350. This circuit 350 is replaced with a lamp current detection circuit 60, an operation switch circuit 62, and a frequency modulation circuit 50 in the embodiment (FIG. 1),
Moreover, it is compatible with the removal of the starting timer circuit 64 of the embodiment of FIG. To this end, it has an operational amplifier 352, an NPN transistor 354, zener diodes 356, 358 and a capacitor 360.

Frequency control circuit 350 detects low current during start-up and ramps high voltage pulses to transformer 56 (Fig. 1) prior to ignition.
18 (FIG. 1), and causes an increase in frequency as the current increases after lighting. Lamp transformer 56 (first
The circuit reaches a stable oscillating state when the leakage inductance in (Fig.) Reduces the current and stabilizes it at a specific frequency.

To detect the current through the lamp 18 (FIG. 1), zener diodes 356, 358 are part of a current detection circuit similar to circuit 60 and are connected back to back in series. The cathode of the Zener diode 358 is electrically connected to the terminal 196, and the cathode of the Zener diode 356 is electrically connected in series to the non-inverting input terminal of the operational amplifier 352 via the first resistor 362 and the second resistor 364. It is connected.

It is electrically connected to the cathode of the Zener diode 358 and the terminal 196 via the capacitor 366, and to the AC ground via the lamp current detection resistor 370. The resistance value of the resistor 370 varies depending on the type of the inserted lamp. The rectifying action of the emitter-base junction of transistor 354, whose base is connected to the junction of resistors 362 and 364, is
And a negative (average) DC control voltage to the non-inverting input of amplifier 352 in response to an AC voltage drop across resistor 370 due to AC current through the lamp.

The inverting terminal of the operational amplifier 352 is connected to the capacitor 36 in order to feed back the voltage to the inverting terminal of the operational amplifier 352 and slow the rise time to give a potential.
It is electrically grounded to the output terminal of the operational amplifier 352 via 0 and to the ground via the resistor 372. Operational amplifier 352
The output terminal of is also electrically connected to the resistor 372 via the resistor 374 and to the cathode of the diode 390 via the resistor 378.

The non-inverting input terminal of amplifier 352 receives the reference potential from the adjustable wiper of lamp current setting potentiometer 388. The end of the wiper is connected between the internal reference source 382 (Fig. 13) in the gated pulser circuit 52 and AC ground.

The output terminal of operational amplifier 352 is electrically connected to the cathode of diode 390 to provide a frequency controlled current signal to gated pulser circuit 52 (FIG. 1). The anode of diode 390 is connected to oscillator 140 at terminal 148A (Fig. 3). Terminal 148A is connected to AC ground through resistor 392 to set a minimum frequency for oscillator 140 when diode 390 is biased off.

Depending on the lamp being turned on after starting, the lamp current is
A voltage drop is generated across both ends of the capacitor and an alternating current is applied through the resistor 362. This alternating current is rectified by the base-emitter junction of transistor 354. The negative average potential obtained at the base of transistor 354 is sent via resistor 364 to the non-inverting input of amplifier 352. This causes the output of amplifier 352 to quickly become more negative, turning on diode 350 through resistor 378. This increases the current through terminal 108.
Terminal 108 is connected to input 148 which controls the frequency of oscillator 140 (FIG. 3). Therefore, the oscillator 140 is a resistor 370.
The frequency is increased in response to the flow of lamp current through the.

Transistor 354 has its base electrically connected to current sense resistor 370 via resistor 362 to provide a shutoff signal to the other conductor 152 of error amplifier 150 in gated pulser circuit 52 when the lamp does not start (FIG. 3). Connected, the emitter is grounded, and the collector is electrically connected to conductor 152 via resistor 392. The conductor 152 is electrically grounded via the capacitor 394, and is also electrically connected to the reference potential source 382 via the resistor 396. By connecting the reference potential to a voltage divider consisting of resistors 380A and 386,
Other conductors 154 of the error amplifier in the gated pulser circuit 52
Given to. These are connected between the reference potential source 382 and AC ground.

The lamp turn-on turns on the base emitter junction of transistor 354 as previously described, clamping the collector potential to AC ground. This leaves capacitor 394 discharged by conduction through resistor 392, and conductor 1
Hold 52 until the potential rises. If the lamp fails to light, the capacitor 394 will charge through resistor 396. When the potential of conductor 152 exceeds that of conductor 154, error amplifier 150 (FIG. 3) causes comparator 124 to set latch 122 and turn off the output transistor and lamp 18.

FIG. 14 is a diagram showing another embodiment of the light source control circuit 450. This circuit 450 includes a blanking pulse generator 452, a frequency and current control circuit 454, a lamp current detection circuit 60A, and an operation switch circuit 62A. The frequency and current control circuit 454 does not require the frequency modulation circuit 50, nor does the current regulation circuit 42 (FIG. 1).

In this circuit, the current from the lamp 18 flows to the lamp current detection circuit 60A via the current sensor. This detection circuit 60A
Has a lamp non-rectifying circuit and a lamp (secondary transformer) current detecting resistor 468, and is similar in configuration to the current detecting circuit 60 in FIG. This non-rectifying circuit has first and second back-to-back Zener diodes 458 and 460, and a capacitor
One plate of 462 is electrically connected to the cathode of Zener diode 458 and the other plate is electrically connected to the cathode of Zener diode 460. The cathode of the Zener diode 460 is electrically connected to the lamp 18, and the cathode of the Zener diode 458 is electrically connected to the detection resistor 468. The other end of this resistor is connected to AC ground via conductor 456.

The operation switch circuit 62A includes a transistor 464 and a resistor 46.
6, including resistor 476 and capacitor 482. The cathode of the Zener diode 458 is electrically connected to the base of the transistor 464 via the resistor 466, and is also electrically connected to one end of the secondary winding of the lamp transformer 56 via the resistor 468. With this configuration, the current flowing through the secondary side of the lamp transformer 56 flows through the conductor 468A to one end of the resistor 468, and the current flowing from the other end of the secondary side of the lamp transformer 56 flows through the lamp 18 to the resistor 468. Flows to the other end, transistor 464
Control.

In order to cut off the power when the lamp does not light,
The emitter of the NPN transistor 464 is grounded, and the collector is connected through the resistor 476 to the input terminal 152 of the gated pulser circuit 52.
It is connected to the. Conductor 382 generated in this circuit 52
The reference potential source above is electrically (1) to the input leads and terminals 152 via resistor 480, (2) to conductors 149 and 154 via resistor 600, and (3) to AC ground via resistor 601. It is connected to the. The terminal 152 is also connected to the ground via the capacitor 482.

With this configuration, the oscillator 140 (FIG. 3) in the gated pulser circuit 52 is prohibited. In this embodiment resistor 144B (FIG. 3) is disconnected to open the collector of transistor 144. The frequency is controlled by externally triggering flip-flop 120 in gated pulser circuit 52 via conductor 416A (FIGS. 3 and 14). This trigger is performed by the trigger circuit 470 which is a part of the frequency / current control circuit 454. Trigger circuit 470
Is a resistor, potentiometer 501-510, transistor 47
2 and 474, diode 514, and positive potential sources 280A and 280B
It consists of.

Diode 513 and capacitor 511 insulate circuit 470 from voltage and reverse current spikes from transformer 56. resistance
501 and potentiometer 502 form a voltage divider across the primary current sensing resistors 290A and 292A of the transformer. When the lamp is on, the primary current is proportional to the lamp current on the secondary side of the transformer. The position of switch 282A determines the lamp operating current and is set according to the type of lamp used.

Immediately after turn-on, the primary current begins to rise, or "ramps up". The voltage is divided between one end of resistor 501, which is connected to the emitter of transistor 472, and the adjustable wiper of potentiometer 502, so that the voltage across the current sense resistor is the base of transistor 472.
When the emitter turn-on voltage is exceeded, current from the collector turns on transistor 474.

A positive trigger and blanking voltage is then applied to terminals 416A and 76 of gated pulser 52, turning off both outputs 70 and 72. These correspond to the same numbered inputs of the switching output circuit (Fig. 1), which turns off the primary current at terminals 82 and 84 (Fig. 2), producing a high voltage pulse on the secondary side. This has a larger effect than the above when 0.7 amperes when the primary current rises to about 1 amperes.
Is set to trigger the primary current to turn on.

The current generated by the trigger is essentially the maximum or peak primary current. Transistor 4 through resistor 505
Because of the positive feedback ("hysteresis") provided by the connection of the base of transistor 472 to the collector of 74,
Gate and pulse circuit for trigger and blanking voltage
While still applied to 52, keep switching transistors 61 and 63 (FIG. 2) off until the primary current begins to drop.

It passes across the primary side of transformer 56 as the triggering process at terminal 416A toggles flip-flop 120 in gated pulser circuit 52 when current is restored.
On successive cycles, the current always rises to the same magnitude and the triggering action described above occurs again accordingly.

As the lamp 18 lights up and warms, its impedance decreases and the trigger time automatically decreases, keeping the peak current at the same magnitude. Thus, frequency control is essential. It is because the leakage inductance of the lamp transformer 56 increases the effective transformer series impedance of the transformer,
This is because the current is reduced to the magnitude set by adjusting the wiper of the potentiometer 502.

The operating primary or modified operating current of the lamp 18 at a predetermined frequency between 100 and 100,000 hertz is sufficient to generate the trigger potential. This trigger potential causes the oscillator to generate pulses at a predetermined frequency. The waveform of the operating current approximates a triangular or sawtooth wave, and the trigger current is about twice the average current. The effective lamp power is set by this average current. The drive circuit includes an inductive reactance (transformer leakage reactance) and a trigger circuit. The trigger circuit increases the frequency of the drive pulse as the current through the lamp increases. The transformer has sufficient inductance to limit the current to the desired operating current of the lamp at practical operating frequencies.

At the starting frequency, the amplitude of the starting voltage is controlled by the magnetizing inductance and the leakage inductance plays no significant role other than loss and capacitive effects. However, at the operating frequency, the leakage inductance controls the current through the lamp and the operating conditions. Due to these factors, in the conventional tube of the embodiment shown in FIG. 14, the ratio of the operating frequency to the start frequency is the ratio of the magnetizing inductance of the primary winding to the leakage inductance of the primary winding.
It is in the range of 1/5 to 10 times.

The blanking pulse generator 452 includes an oscillator to provide the blanking pulse to the lamp 18. This oscillator is a CMOS integrated circuit equivalent to the TTL embedded integrated circuit oscillator shown in FIG. 1 and has two comparators 484 and 486.
And a flip-flop step. This flip-flop stage is a cross-coupled NOR powered by a potential source 400.
It has a gate 488. The output from the cross-coupled NOR gate is applied to resistor 492 via conductor 420B in FIG. 14 (similar to conductor 420A in FIG. 11) and to the base of blanking pulse transistor 494.

The collector of blanking pulse transistor 494 is electrically connected to terminals 76 and 416A via diode 418B to provide a blanking and synchronization output to gated pulse circuit 52. Positive potential source 280A provides a potential for this through resistor 424A. The input 70E to the comparator 484 is the conductor 70C,
It is connected to the input terminal 70 via the capacitor 70B and the resistor 70A, and applies a return synchronization pulse to the gated pulser circuit 52. The blanking pulse terminates generator 452.
Following each blanking pulse, the trigger circuit 470 causes the transistor to conduct, following the blanking pulse until the primary current is sufficient to store sufficient energy in the magnetic field of the transformer to relight the lamp. The warm-up timer 413 (FIG. 10) is not required in the embodiment of FIG.

In each embodiment, the magnetizing inductance of the lamp transformer 56 at the start frequency is small enough so that current will flow through the lamp 18 at the start frequency for less than half of this time. The operating frequency is also sufficiently high so that the shock coefficient at this operating frequency is at least twice the shock coefficient at the starting frequency. Suitably, the duty cycle at the operating frequency is at least 50%.

From the above description of FIG. 14, the operating current through the lamp is detected in the primary circuit of the transformer and directly in the secondary circuit of the lamp. This is also true for most of the transition period between start and run. Of course, this can be applied to the opposite situation where the secondary current is an indicator of the primary current.

From the above description, it is understood that the absorption monitor of the present invention has some effects. For example, (1) the present invention does not require a separate high voltage transformer for starting zinc or cadmium lamps, (2) the present invention has a fairly low noise output, (3) the present invention is a worm. After the upgrade, do not be affected by the oscillation in the lamp, (4)
The present invention is inexpensive and reliable, and (5)
The present invention is the use of a small, low cost and light transformer.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an electric circuit diagram of a part of the embodiment of FIG. 1, and FIG. 3 is an electric circuit diagram of another part of the embodiment of FIG. FIG. 4 is an electric circuit diagram of still another part of the embodiment shown in FIG. 1, FIG. 5 is an electric circuit diagram of yet another part of the embodiment shown in FIG. 1, and FIG. 6 is an electric circuit diagram of the embodiment shown in FIG. FIG. 7 is an electric circuit diagram of still another part of the embodiment shown in FIG. 1, and FIG. 8 is an electric circuit diagram of another part of the embodiment shown in FIG. 9 is the eighth
FIG. 10 is a partial electric circuit diagram of the embodiment shown in FIG. 1, FIG. 10 is a partial electric circuit diagram of another embodiment of the embodiment shown in FIG.
FIG. 12 is a logic circuit diagram of a portion of the circuit shown in FIG. 12, FIG. 12 is an electric circuit diagram of another portion of the embodiment shown in FIG. 1, and FIG. 13 is another portion of an embodiment of the present invention incorporating the circuit shown in FIG. Electrical schematic of the
FIG. 14 is an electric circuit diagram of another embodiment of the present invention. 10: Absorption monitor, 12: Dual beam optical system, 14: Light source control circuit, 16: Detection and recording device, 18: Lamp, 20, 22: Flow cell, 24, 26: Photocell, 40: Start control circuit, 42: Current Adjustment circuit, 44: frequency and drive control circuit, 50: frequency modulation circuit, 52: gated pulser, 53: synchronization and blanking circuit, 54: switching output circuit, 56: lamp transformer, 60: lamp current detection circuit, 62 : Operation switch circuit, 6
4: Start timer circuit, 82, 84: Output terminal

Claims (19)

[Claims] 1. A circuit for operating a gas discharge lamp used for an absorption monitor, comprising a primary winding (82, 84) and a gas discharge lamp (18) and a secondary winding in a circuit state. A switching circuit (5) including a lamp transformer (56) and a current blocking device (86, 88) to generate a sufficiently high potential.
In a circuit including a pulse circuit (52) for applying a pulse to the primary windings (82, 84) via 4), the lamp current detector (60) is a starting device when a low lamp current is detected. In this starter, the pulse circuit (52) outputs a long pulse to the primary winding (82, 8).
4) and a current pulse is applied to the lamp transformer (5
Stopping the flow of current to the primary winding after continuing to be applied to 6), the lamp transformer (56) is at least 20 kOhms on the secondary side of the lamp transformer, and Sufficient to store enough energy to generate a pulse with an amplitude of at least 1000 volts with a pulse width of at least 10 microseconds from an average current flowing through the primary side corresponding to an input power load of less than 5 times the operating power. Having high inductance and low loss, a high potential spike is applied across the gas discharge lamp (18) to start it and the frequency modulator (50) as the current increases to a predetermined operating value. A circuit for operating a gas discharge lamp used in an absorption monitor, characterized in that the frequency of the pulse is increased. 2. A circuit according to claim 1, wherein the frequency modulator (50) increases the voltage of the pulse as the current increases during starting and the current reaches a predetermined value. The lamp current detector (60) which later limits the current
A circuit characterized by being controlled by. 3. A circuit according to claim 1 or 2, wherein the lamp (18) is at least at an operating voltage of 3.
A circuit characterized by being activated by double the initial lighting voltage. 4. A circuit as claimed in any one of claims 1 to 3, in which the current is below a first predetermined value.
The start-up timer circuit (64) takes the timing of the time period until a predetermined value of is reached, and when the current does not reach the second predetermined value, the interruption stage (156)
Circuit that terminates the pulse. 5. A circuit as claimed in any one of claims 1 to 4, characterized in that one of the transformers (56) is present for a period of time at least equal to the time required for the continuous generation of two pulses. A circuit characterized in that a synchronization and blanking circuit (53) for blanking a pulse is provided on the next winding (82, 84). 6. The circuit according to any one of claims 1 to 5, wherein the warm-up timer (413) is at least 2 seconds from the start of applying the pulse to the transformer (56). A circuit characterized by blocking blanking during a time period of. 7. The circuit according to any one of claims 1 to 6, wherein the primary winding (82, 84) has a center tap and first and second end taps. As a result, the current flows through the primary side in one of two directions, and the switching circuit (54) causes the transistor (61, 63) to
Has a current flowing in one direction and a current in the other direction is cut off, the current from the transformer (56) in one direction is stopped, and the current is alternately supplied from the current source in the other direction. Flow, which causes the energy of the magnetic field to be alternately discharged into the secondary circuit first in one direction and then in the other,
As a result, a high potential peak is generated from the induced magnetic field in the transformer (56).
A starting control circuit (40) for sending current to the secondary winding of the coil forms a voltage peak having a switching time and an inductance of the primary winding of at least 1000 volts before the lamp conducts. A circuit characterized by including a starting timer circuit (64). 8. A circuit as claimed in any one of claims 1 to 7, characterized in that the transformer (56) is pulsed for a time period longer than twice the normal operating pulse duration.
A circuit characterized in that a synchronization and blanking circuit (53) for blanking is provided on the primary side (82, 84) of the. 9. A circuit according to claim 1, wherein the lamp (18) has a variable impedance after being lit in response to an operating current through the lamp (18). A circuit characterized in that the circuit (272) blocks high voltage peaks greater than the peak voltage of the lamp (18). 10. A circuit according to any one of claims 1 to 9, wherein a frequency and current control circuit (454) for controlling current to a first predetermined level is provided.
A trigger circuit (454) in which the frequency and current control circuit (454) detects the current and alternately stops the flow of current from the current source each time the magnitude of the current increases to the trigger level of the trigger circuit (470). 470), whereby the lamp (18) inherently starts at a low frequency under the influence of a large voltage spike from the transformer (56) and the frequency is increased as the lamp (18) is started. A circuit characterized in that it inherently rises to the required extent so that the series impedance represented by the leakage inductance of the transformer (56) regulates the current to a first predetermined value. 11. The circuit according to any one of claims 1 to 10, wherein the primary side of the transformer has a center tap, and the switching circuit (54) alternates with the first tap. A circuit characterized by blocking current during one half-cycle, while allowing current to flow during the second half-cycle, and blocking current during the second half-cycle while flowing current during the first half-cycle. 12. A circuit as claimed in any one of claims 1 to 11, characterized in that the switching circuit (54) is connected in each case to another end of the winding of the transformer. First and second power switches (61,63) having first and second control elements (70,72) present, and connected to said first and second control elements (70,72) A flip-flop (120) for alternately driving one of the first and second power switches (61, 63) to be conductive and the other to be non-conductive, and to drive the first and second power switches. Switch (61,6
3) A circuit having a flip-flop (120) that drives one of them to be conductive and the other to be non-conductive. 13. A circuit as claimed in any one of claims 1 to 12, in which the flip-flop (120) is for a short time period of at least 2 seconds after a pulse is applied to the transformer. A circuit having an oscillator (140) for periodically disabling the circuit. 14. A method for operating a gas discharge lamp used for an absorption monitor with a pulse having a predetermined amplitude via a lamp transformer (56), wherein a dead section of zero current amplitude is provided between the pulses having the predetermined amplitude. And the current from the transformer (56) is discharged to the lamp (18) during the starting period of the lamp (18) and during the dead zone, the transformer (56) being sufficient for this purpose. An average having a high inductance and a low loss, flowing through the primary side corresponding to an input power load of less than 5 times the normal operating power, between at least 20 kOhm resistance on the secondary side of the lamp transformer. Energy is accumulated from the current to form a pulse with an amplitude of at least 1000 volts with a pulse width of at least 10 microseconds, the lamp being charged until the current reaches a predetermined frequency. (1
8) A method of operating a gas discharge lamp for use in an absorption monitor, comprising the steps of increasing the frequency of the pulse passing through the transformer (56) as the current passing through 8) increases. 15. The method according to claim 14, wherein the time from the start of the start cycle is measured and the start of the start if the current through the lamp (18) does not reach a predetermined amplitude. After a lapse of a predetermined time from the start, the start control circuit (40) is cut off, and the transformer (56) is until the current reaches a predetermined frequency.
A method comprising increasing the frequency of a pulse passing through. 16. Method according to claim 14 or 15, characterized in that a short blanking pulse is applied to the lamp (18) to prevent baseline noise. 17. A method as claimed in any one of claims 14 to 16 comprising timing for a period of at least 2 seconds from start and inhibiting the blanking pulse during said time. How to characterize. 18. The method according to claim 14, wherein the step of applying a pulse of a predetermined amplitude through the lamp transformer (56) comprises a constant current source (60). ) And applying a pulse via the primary side (82, 84) of the lamp transformer (56). 19. A method according to any one of claims 14 to 18, wherein the step of applying a pulse of a predetermined amplitude through the transformer (56) of the lamp comprises the step of: Between a primary winding (82, 84) of a transformer (56) having in its circuit a gas lamp having an inductive circuit, an induction circuit, and an oscillator (140) generating a frequency that increases according to the current flowing in the circuit. Applying a potential to the circuit, wherein the inductance of the circuit, the potential and the oscillator characteristic are adjusted in accordance with a predetermined voltage such that the inductance provides a frequency that limits the operating current of the lamp. .